The handling of metal strips or metal sheets in a metal working industry involves transportation thereof along different processing lines, such as for example hot-dip galvanizing lines. The metal strips are prone to vibration during the movements owing to their relative thinness and elongated shape and due to a number of sources of vibration. Vibrations occur, among other things, due to imperfections in the line's mechanical components, and due to different process steps, for example air-knife actions used for blowing off excess zinc from the metal strips after a galvanization step. The transportation of the metal strips therefore requires stabilization.
Without stabilization, the metal strips would be subject to shape loss, e.g. bending, and several processing steps would be less efficient. For example, the lack of vibration control during the mentioned air-knife actions would result in variable thickness of the zinc coating and thus lessened product quality and increased costs. The processing of the metal strips would thus be rendered inefficient and expensive. The importance of controlling the movements of the metal strips is thus readily realized.
Published International patent publication WO 2009/030269 discloses a method for stabilizing and controlling the vibrations of metals strips. The profile of the metal strip is controlled by a plurality of non-contact actuators based on a combination of mode shapes, wherein the combination of mode shapes approximates the metal strip profile. The metal strip profile and the forces acting on the metal strip are expressed as combinations of the mode shapes, using the same number of mode shapes as there are actuators.